NASA Captures Stunning Image of Pluto's Occultation

At the 227th meeting of the American Astronomical Society last week, there was lots of buzz surrounding what was once the galaxy's 9th planet. After the historic flyby last summer, we're finally starting to get some insight into Pluto's composition and environment. Now it has been revealed that just before that flyby, SOFIA, NASA's flying observatory, snapped a beautiful image of Pluto's occultation, providing the space agency with an unprecedented look at Pluto's atmosphere.

Earlier in 2015, NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) managed to be in exactly the right place at exactly the right time. It captured Pluto's passage in front of a star, an event known as an occultation (in layman's terms, an eclipse). This occultation caused a faint shadow of Pluto to move across the surface of the Earth, creating an amazing opportunity for scientific analysis.

But the conditions had to be just right in order for this to happen. The shadow moved at more than 53,000 mph, meaning that calculations and timing for SOFIA had to be perfect in order to seize the opportunity. The occultation also might not have happened to fall on a telescope, meaning that scientists wouldn't have been able to gather any data. It might have been cloudy during the 120 second observation window. Luckily, using SOFIA eliminated most of these problems; capable of cruising at 45,000 feet, the mobile observatory gets above the clouds and can easily fly over just about any location on Earth, including oceans.

Luckily, the stars aligned, so to speak, and the team behind SOFIA managed to get it in place in time to collect detailed measurements of Pluto's atmospheric density and structure. Though the occultation data is currently available to members of NASA's New Horizon's mission, it will open to the general public in July 2016.

During the AAS meeting (via Space.com), Michael Pearson, a research scientist at MIT, explained why capturing and measuring this event is so important:

"When [an occultation] happens with Pluto, we can watch the interaction between the light from the star and Pluto's atmosphere, and learn about the atmosphere from Earth-based measurements without having to actually go out there and see what's going on."

Though scientists have been studying Pluto occultations for decades, the one in June 2015 was the first to have the potential to affect all subsequent studies of Pluto. That's because two weeks after SOFIA's voyage, the New Horizon's probe was set to become the very first space probe to make a close encounter with Pluto. As a result, scientists could use the data collected from New Horizon in comparison with the occultation data in order to better understand what they were seeing on Earth.

"If we could get a stellar occultation during the weeks when New Horizon was passing by Pluto, we could calibrate decades worth of data against what New Horizon was seeing... and put everything on the same fundamental basis," said Pearson.

SOFIA's flight combined with New Horizon's data contributed a growth of understanding of Pluto's atmosphere, including evidence that showed that Pluto's atmosphere isn't collapsing the farther away it moves from the sun. Though New Horizon will never fly by Pluto again, scientists will continue to observe occultations from Earth for years, and the comparison made will allow them to keep an eye on Pluto's changing atmosphere.